43 lines
2.0 KiB
Plaintext
43 lines
2.0 KiB
Plaintext
KVM CPUID bits
|
|
Glauber Costa <glommer@redhat.com>, Red Hat Inc, 2010
|
|
=====================================================
|
|
|
|
A guest running on a kvm host, can check some of its features using
|
|
cpuid. This is not always guaranteed to work, since userspace can
|
|
mask-out some, or even all KVM-related cpuid features before launching
|
|
a guest.
|
|
|
|
KVM cpuid functions are:
|
|
|
|
function: KVM_CPUID_SIGNATURE (0x40000000)
|
|
returns : eax = 0,
|
|
ebx = 0x4b4d564b,
|
|
ecx = 0x564b4d56,
|
|
edx = 0x4d.
|
|
Note that this value in ebx, ecx and edx corresponds to the string "KVMKVMKVM".
|
|
This function queries the presence of KVM cpuid leafs.
|
|
|
|
|
|
function: define KVM_CPUID_FEATURES (0x40000001)
|
|
returns : ebx, ecx, edx = 0
|
|
eax = and OR'ed group of (1 << flag), where each flags is:
|
|
|
|
|
|
flag || value || meaning
|
|
=============================================================================
|
|
KVM_FEATURE_CLOCKSOURCE || 0 || kvmclock available at msrs
|
|
|| || 0x11 and 0x12.
|
|
------------------------------------------------------------------------------
|
|
KVM_FEATURE_NOP_IO_DELAY || 1 || not necessary to perform delays
|
|
|| || on PIO operations.
|
|
------------------------------------------------------------------------------
|
|
KVM_FEATURE_MMU_OP || 2 || deprecated.
|
|
------------------------------------------------------------------------------
|
|
KVM_FEATURE_CLOCKSOURCE2 || 3 || kvmclock available at msrs
|
|
|| || 0x4b564d00 and 0x4b564d01
|
|
------------------------------------------------------------------------------
|
|
KVM_FEATURE_CLOCKSOURCE_STABLE_BIT || 24 || host will warn if no guest-side
|
|
|| || per-cpu warps are expected in
|
|
|| || kvmclock.
|
|
------------------------------------------------------------------------------
|